We are interested in how bacteria and bacterial products shape the development of subsequent innate and adaptive immune responses with the goal of understanding how these host-microbe interactions influence pathogenesis of infections, autoimmunity, allergy, and cancer. We have continued our focus on host defense against the bacterial pathogen Staphylococcus aureus, uncovering the role of innate and adaptive immune pathways in mediating protective and detrimental responses to infection using mouse models, and characterizing these responses in human clinical studies. In addition, we have identified influences of host-commensal interactions on susceptibility to infections and immune responses. This has led to a new discovery of a bacteria that is safe, but has the ability to improve eczema (atopic dermatitis) symptoms in patients with this disorder. With these studies we have enhanced our understanding of the mechanisms controlling skin and mucosal host defense and identified potential pathways that can be targeted to enhance efficacy of vaccines and therapies against cancer, infection, and immune-mediated diseases.